The present invention concerns polymers prepared by reacting a heterocyclic material having one or more rings and 1 nitrogen atom therein or mixtures thereof wherein at least one of such material contains at least 2 reactive substituent groups which have at least one hydrogen atom attached to a carbon atom which is attached to the heterocyclic ring with cycloaliphatic or aromatic carboxylic acid mono or dianhydrides.
It has been shown by Manly et al in J. Org. Chem., 1958, Vol. 23, pp. 373-380 that indanediones can be prepared by reacting dimethylpyridines with phthalic anhydride. He also stated that 2-methylpyridine reacted with phthalic anhydride to form pyrophthalone.
Ogata in Japanese Pat. No. Sho 42(1967)-14468 prepared polymers that melt above 500.degree. C. by reacting pyridine having methyl substituents with pyromellitic dianhydride.
The present invention provides polymers by the reaction of nitrogen containing heterocycles having at least two reactive substituent groups which have at least one hydrogen atom attached to a carbon atom which is attached to the nitrogen-containing heterocyclic ring and one nitrogen atom with carboxylic acid mono or dianhydrides. Polymers with melting points less than 300.degree. C. can be obtained by the reaction of an aromatic heterocyclic material containing one nitrogen atom having such reactive substituent groups with dicarboxylic acid monoanhydrides, or by the reaction of the aromatic nitrogen containing heterocycle having such reactive substituent groups with a tetracarboxylic acid dianhydride or by addition of an aromatic nitrogen containing heterocycle having one such reactive substituent group or a dicarboxylic acid monoanhydride as chain terminators, or no catalyst, or limiting the reaction time, or an excess of one of the reactants. These prepolymers can be homopolymerized or copolymerized with a N,N'-bis-imide to give thermoset products with good thermal properties as well as good physical properties.
The resin or resin mixture softens below 300.degree. C., preferably below 200.degree. C., which provides for ease of processing the prepolymers as homopolymeric materials or as copolymers with N,N'-bis-imides. For a resin to obtain its greatest utility it must be moldable. Molding of resins is convenientally done at or about 200.degree. C. or below. The resins produced from a nitrogen containing heterocycle with at least two reactive substituent groups and a tetracarboxylic acid dianhydride must have softening points at or about 200.degree. C. or below in order to find their greatest use in forming composites of the homopolymer by solution or hot melt prepregging, in blending with N,N'-bis-imides to form copolymers, or in forming composites from the N,N'-bis-imide copolymers. The prepolymers discussed in this patent and the copolymers made by addition of N,N'-bis-imides all have softening points at or about 200.degree. C. or below.